U.S. patent number 6,293,514 [Application Number 09/600,646] was granted by the patent office on 2001-09-25 for flow regulation valve.
This patent grant is currently assigned to A. Theobald SA. Invention is credited to Christophe Pechoux, Claude Villermaux.
United States Patent |
6,293,514 |
Pechoux , et al. |
September 25, 2001 |
Flow regulation valve
Abstract
A valve including a cylindrical bore having a circular seat at
one end thereof, a valve member that is movable in the axial
direction of the seat, and control means connected to the valve
member, the valve member including a first portion which serves as
a closure element, and a second portion which is engaged in the
bore and which is shaped to regulate the flow of the fluid at a
desired rate depending on the axial position of the valve member,
the second portion of the valve member is detached from the first
portion and has a cylindrical outside surface of diameter such that
it is in sliding contact with the cylindrical surface of the bore;
at least one recess is formed in the cylindrical outside surface of
the second portion of the valve member so as to define a passage
having a predefined shape, and means is provided for permanently
holding the two portions of the valve member in mutual contact so
that they are displaced axially simultaneously under the action of
the control means.
Inventors: |
Pechoux; Christophe (Torcy,
FR), Villermaux; Claude (Chatillon sous Bagneux,
FR) |
Assignee: |
A. Theobald SA
(FR)
|
Family
ID: |
9521980 |
Appl.
No.: |
09/600,646 |
Filed: |
July 20, 2000 |
PCT
Filed: |
January 21, 1999 |
PCT No.: |
PCT/FR99/00118 |
371
Date: |
July 20, 2000 |
102(e)
Date: |
July 20, 2000 |
PCT
Pub. No.: |
WO99/37943 |
PCT
Pub. Date: |
July 29, 1999 |
Foreign Application Priority Data
|
|
|
|
|
Jan 21, 1998 [FR] |
|
|
98 00593 |
|
Current U.S.
Class: |
251/122;
137/625.3; 251/129.08; 251/129.19; 251/205; 251/54 |
Current CPC
Class: |
F16K
1/52 (20130101); F16K 31/0689 (20130101); Y10T
137/86734 (20150401) |
Current International
Class: |
F16K
31/06 (20060101); F16K 1/32 (20060101); F16K
1/52 (20060101); F16K 001/52 (); F16K 031/06 () |
Field of
Search: |
;251/118,120,121,122,77,84,54,205,129.08,129.19 ;137/625.3 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Shaver; Kevin
Assistant Examiner: Keasel; Eric
Attorney, Agent or Firm: Webb Ziesenheim Logsdon Orkin &
Hanson, P.C.
Claims
What is claimed is:
1. A valve for regulating the flow of a liquid or gaseous fluid,
the valve comprising:
a body having an inlet and an outlet for the fluid;
a partition which separates the inlet from the outlet and which
includes a cylindrical bore having a circular seat at one end
thereof;
a valve member that is movable in the axial direction of the
circular seat between first and second positions in which the valve
is respectively closed and open; and
control means functionally connected to said valve member in order
to bring it into any desired axial position between its first and
second positions so as to regulate the flow of the fluid, said
valve member including a first portion which serves as a closure
element when the valve member is in its first position, and a
second portion which is engaged in said bore and which is shaped to
regulate the flow of the fluid at a desired rate depending on the
axial position selected for the valve member between its first and
second positions,
wherein the second portion ofthe valve member is detached from the
first portion of the valve member and the second portion has a
cylindrical outside surface diameter such that the second portion
of the valve member is in sliding contact without friction with the
cylindrical surface of said bore, and the second portion of the
valve member includes means for bringing the first and second
portions of the valve member closer together so as to produce a
simple mutual contact and to hold the contact permanently so that
the first portion of the valve member and the second portion of the
valve member are displaced axially simultaneously and by the same
amount under the action of the control means.
2. The valve as claimed in claim 1, wherein the first portion of
the valve member is functionally connected to the control means,
and wherein the means which holds the first and second portions of
the valve member in mutual contact is constituted by a spring which
pushes the second portion of the valve member axially against the
first portion of the valve member.
3. The valve as claimed in claim 1, wherein the first portion of
the valve member is functionally connected to the control means,
and wherein the means which holds the first and second portions of
the valve member in mutual contact is constituted by a permanent
magnet which is carried by one of the first and second portions of
the valve member, the other portion being made, at least in part,
of a magnetizable material.
4. The valve as claimed in claim 1, wherein the control means
comprises an electromagnet that is excited by approximate AC and
including a moving core that is connected via a rod to the valve
member of the valve, the electromagnet being associated with a
return spring which holds the valve member in its first position in
the absence of the electromagnet being excited, and with a
hydraulic damper which controls the displacement of the valve
member resulting from the electromagnet being excited.
5. The valve as claimed in claim 1, wherein the second portion of
the valve member includes at least one recess formed in the
cylindrical outside surface of the second portion of the valve
member so as to define a passage having a predefined shape.
6. The valve as claimed in claim 5, wherein the passage has a flow
section which varies in said axial direction.
7. The valve as claimed in claim 6, wherein the second portion of
the valve member is constituted by a hollow cylindrical element
having a peripheral wall which includes, by way of varying-section
passage, at least one longitudinal slot or notch which has a
varying width in the longitudinal direction of the hollow
cylindrical element.
8. The valve as claimed in claim 6, wherein the second portion of
the valve member is constituted by a cylindrical element, the
cylindrical outside surface of which is formed, with a
varying-section passage having at least one longitudinal groove
having a width and depth which varies in the longitudinal direction
of the cylindrical element.
9. The valve as claimed in claim 6, wherein the second portion of
the valve member is constituted by a cylindrical element, the
cylindrical outside surface of which is formed, with a
varying-section passage having at least one longitudinal groove
having a width which varies in the longitudinal direction of the
cylindrical element.
10. The valve as claimed in claim 6, wherein the second portion of
the valve member is constituted by a cylindrical element, the
cylindrical outside surface of which is formed, with a
varying-section passage having at least one longitudinal groove
having a depth which varies in the longitudinal direction of the
cylindrical element.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve for regulating the flow of
a liquid or gaseous fluid, the valve being of the type including a
body having an inlet and an outlet for the fluid, a partition which
separates the inlet from the outlet and which includes a
cylindrical bore having a circular seat at one end thereof, a valve
member that is movable in the axial direction of the circular seat
between first and second positions in which the valve is
respectively closed and open, and control means functionally
connected to said valve member in order to bring it into any
desired axial position between its first and second positions so as
to regulate the flow of the fluid, said valve member including a
first portion which serves as a closure element when the valve
member is in its first position, and a second portion which is
engaged in said bore and which is shaped to regulate the flow of
the fluid at a desired rate depending on the axial position
selected for the valve member between its first and second
positions.
2. Description of the Prior Art
Known valves described in documents U.S. Pat. No. 3,108,777 and
FR-A-2 650 362, for example. In those two documents, the first
portion of the moving valve member is substantially in the form of
a disk and is connected via a rod to the moving core of an
electromagnet serving as control means. When the coil of the
electromagnet is not excited, the valve member is held by a return
spring in its first position or valve-closed position. In known
electrically-controlled valves, the second portion of the valve
member is constituted by a part which is a body of revolution about
the axis of the rod, e.g. a truncated cone, and which is fixed
securely to the first portion of the valve member. Thus, by giving
a predefined shape to the generator lines of the surface of
revolution which constitutes the outside surface of the second
portion of the valve member, it is possible, in principle, to
obtain any desired flow/displacement characteristic when the valve
member is displaced axially. However, in practice, in order to
obtain the desired flow/displacement characteristic in fact, a
valve member of that structure requires the axis of the surface of
revolution to be accurately centered or aligned with the axis of
the circular seat of the valve. This requires high precision when
manufacturing the seat and the valve member, when assembling the
two elements together, and when guiding the control rod of the
valve member, and as a result such a valve is relatively
costly.
Furthermore, in certain fields of use, e.g. in the field of gas
boilers where valves of the above-mentioned type are used as means
for regulating the flow of fuel gas sent to an air/gas mixing
chamber preceding the burner of the boiler, in order to modulate
the flow as a function of the instantaneous heating power required
by the boiler while simultaneously keeping the flow of gas and the
flow of air in a predetermined ratio, it is often desirable for the
flow of gas to be regulated in a manner that is very fine and
smooth, especially in the low-flowrate range, i.e. when the first
portion of the moving valve member is in an axial position that is
very close to the circular seat of the valve. In other words, in
the low-flowrate range, it is desirable that any given axial
displacement of the valve member causes only a small variation in
the flow of fluid passing through the valve, such that the
flow/displacement characteristic of the valve has a shallow slope
in the low-flowrate range. In practice, this is difficult to obtain
with a known electrically-controlled valve of the above-mentioned
type, in which the second portion of the moving valve member has an
outside surface in the shape of a truncated cone.
Furthermore, in known electrically-controlled valves of the
above-mentioned type, it is usual to excite the electromagnet by
means of pure or approximate AC so as to eliminate, at least in
part, the magnetic hysteresis that the electromagnet would exhibit
if it were to be excited by DC. However, exciting the electromagnet
with AC causes the valve member to oscillate, which imparts
oscillations into the flow and the pressure of the gas downstream
of the electrically-controlled valve. Such oscillations are harmful
to the flame of the burner, especially in the low-gasflow range. To
avoid such oscillations, it is thus necessary to associate a
damper, e.g. a hydraulic damper, with the moving equipment
constituted by the electrically-controlled valve member and by the
moving core of its electromagnet, as described in the
above-mentioned American and French patents. It should also be
observed that in the low-flowrate range, when the moving valve
member is very close to its circular seat, the oscillations of the
valve member can also create noise as a result of the repeated
impacts of the valve member on its seat.
That is why the hydraulic damper must be very effective, and as a
result it is relatively complex to make. In particular, the radial
clearance between the piston and the cylinder of the hydraulic
damper must be very small, which requires high mechanical precision
in the machining and assembly of the two elements. Furthermore,
since the presence of the hydraulic damper greatly reduces the
displacement speed of the moving valve member, the
electrically-controlled valve has a response time that is long and
a check-valve must be provided that is connected hydraulically in
parallel with the damper to enable the electrically-controlled
valve member to be closed rapidly whenever the
electrically-controlled valve is also used as a safety valve. In
that case, the safety valve member must be capable of being closed
in less than one second.
For all of the reasons mentioned above, electrically-controlled
valves of the same type as those described in patent U.S. Pat. No.
3,108,777 and FR-A-2 650 362 are described in patent U.S. Pat. No.
3,108,777 and FR-A-2 650 362 are relatively costly. Furthermore,
although the use of pure or approximate AC for exciting the
electromagnet enables the magnetic hysteresis of the electromagnet
to be eliminated at least in part, it does not eliminate mechanical
hysteresis resulting from friction. Since the addition of a
hydraulic damper to the electrically-controlled valve has the
effect of increasing friction, such a damper thus increases
mechanical hysteresis, and the greater the effectiveness of the
damper, the greater the mechanical hysteresis it has.
Unfortunately, for the same reasons as those described in document
FR-A-2 650 362, mechanical hysteresis is a problem when the
electrically-controlled valve is used as a regulating element in a
temperature regulation loop, since it deteriorates the accuracy of
the regulation.
Valves comprising two portions are also known from patents CH 581
284 A (KLEIN SCHANZLIN & BECKER AG), FR 619 503 A (P. PASCALE),
and U.S. Pat. No. 4,125,129 A (BAUMANN HANS D). However, the two
portions are not detached, but are securely connected to each
other.
SUMMARY OF THE INVENTION
Thus, the main object of the present invention is to provide a
valve for regulating the flow of a liquid or gaseous fluid,
enabling the flow of a liquid or gaseous fluid to be regulated
precisely and in accordance with a predefined law as a function of
the axial displacement of its moving valve member, without
requiring high mechanical precision, such that the valve can be
manufactured at a cost that is significantly lower than that of
known valves of the same type.
Another object of the present invention is to provide a valve by
means of which the flow of fluid can be regulated in a fine and
even manner, at least in the low-flowrate range of the
flow/displacement of the valve.
An auxiliary object of the present invention is to provide an
electrically-controlled valve enabling the flow of a fluid under
pressure to be modulated, the valve having a moving valve member
that is excited by pure or approximate AC and that is associated
with a hydraulic damper, the assembly having little magnetic
hysteresis, little mechanical hysteresis, and a better response
time, and being simple and cheap to manufacture.
To this end, in the valve of the invention the second portion of
the valve member is detached from the first portion of the valve
member and has a cylindrical outside surface of diameter such that
it is in sliding contact with the cylindrical surface of the bore,
at least one recess is formed in the cylindrical outside surface of
the second portion of the valve member so as to define a passage
having a predefined shape, and means is provided for permanently
holding the first and second portions of the valve member in mutual
contact so that they are displaced axially simultaneously under the
action of the control means.
Thus, as a result of the first and second portions of the valve
member being detached from each other, the control rod, which is
connected to the first portion of the valve member, no longer needs
to be accurately in alignment with the axis of the circular seat,
and it thus no longer needs to be mounted and guided in an
extremely precise manner. Consequently, manufacture and assembly of
the valve is greatly simplified. Since the second portion of the
valve member is slidably mounted in the cylindrical bore of the
seat, and is in sliding contact with the bore, the second portion
of the valve member remains continuously centered and in good
alignment on the axis of the circular seat, such that it suffices
to give the recess or recesses which is or are formed in the
cylindrical outside surface of the second portion of the valve
member an appropriate shape in order to obtain the desired flowrate
of fluid for each axial position of the second portion of the valve
member relative to the circular seat, so as to obtain the desired
flow/displacement characteristic.
The passage or passages formed by the above-mentioned recess or
recesses preferably has or have a flow section which varies in the
axial displacement direction of the valve member so as to obtain
the desired flow/displacement characteristic. As can be seen below,
the above-mentioned passage or passages can be designed in such a
manner that the flow/displacement characteristic obtained presents
a shallow slope in the low-flowrate region This is particularly
advantageous in the case where the valve is produced in the form of
an electrically-controlled valve controlled by an electromagnet
that is excited with approximate AC, the electromagnet being
associated with a return spring which holds the valve member in its
first position in the absence of the electromagnet being excited,
and with a hydraulic damper which controls the displacement of the
valve member resulting from the electromagnet being excited. In
this case, given that a small displacement of the valve member in
the low-flowrate range causes the flow rate to vary very little, it
becomes possible to tolerate small residual mechanical oscillations
of the valve member. Consequently, the hydraulic damper of the
electrically-controlled valve of the invention does not need to
have a damping power as great as that of prior-art
electrically-controlled valves. As a result, the structure of the
hydraulic damper can be considerably simplified. In particular, the
clearance between the piston and the cylinder of the hydraulic
damper can be about 1 mm, whereas it must be 20.mu. in the damper
associated with known electrically-controlled valves. Furthermore,
since the valve member is braked less by the hydraulic damper, the
response time of the electrically-controlled valve is significantly
improved. Furthermore, the electrically-controlled valve can be
closed rapidly, in natural manner, under the action of the return
spring of the valve member, without it being necessary to mount a
check-valve hydraulically in parallel with the hydraulic damper.
The valve of the invention is thus well suited for being used also
as a safety valve. Finally, the above-mentioned small residual
mechanical oscillations give rise, by a trembling effect, to a
reduction in friction which, combined with the reduction in the
internal friction of the hydraulic damper, almost completely
eliminates mechanical hystereis.
In an embodiment of the present invention, the means which enable
the first and second portions of the valve member to be held
permanently in mutual contact can be constituted by a spring, e.g.
a helical spring, which pushes the second portion of the valve
member axially against the first portion of said valve member.
In another embodiment of the invention, said holding means can be
constituted by a permanent magnet, for example, which is carried by
one of the first and second portions of the valve member, the other
portion thus being made, at least in part, of a magnetizable
material.
BRIEF DESCRIPTION OF THE DRAWINGS
Other characteristics and advantages of the present invention
appear better from the following description given with reference
to the accompanying drawings, in which:
FIG. 1 diagrammatically shows, partially in vertical section and
partially in elevation, an electrically-controlled valve
constituting a first embodiment of the invention, with a moving
valve member composed of two separate portions held in mutual
contact;
FIG. 2 shows, on larger scale and in elevation, one of the two
portions of the valve member of FIG. 1;
FIG. 3 is a fragmentary view in vertical section on line III--III
of FIG. 2;
FIG. 4 is a view along arrow F of FIG. 2;
FIG. 5 is a section view on line V--V of FIG. 4;
FIG. 6 is a graph showing the flow/displacement characteristic of
the electrically-controlled valve of FIG. 1;
FIG. 7 is a fragmentary view of a valve constituting a second
embodiment of the present invention;
FIG. 8 is a perspective view showing one of the two portions of the
moving valve member of the valve of FIG. 7;
FIG. 9 is a graph showing the flow/displacement characteristic of
the valve of FIG. 7;
FIG. 10 is a perspective view similar to FIG. 8 showing a
variant;
FIG. 11 is a graph showing the flow/displacement characteristic of
the valve of FIG. 7 in the case where it is fitted with a moving
valve member having a portion as shown in FIG. 10;
FIG. 12 is a view similar to FIG. 7 showing yet another embodiment
of the present invention;
FIG. 13 is a perspective view similar to FIGS. 8 and 10 showing one
of the two portions of the valve member of the valve shown in part
in FIG. 12; and
FIG. 14 is a graph showing the flow/displacement characteristic of
the valve shown in FIG. 12.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to FIG. 1, the electrically-controlled valve 1 of
the invention generally includes a body 2 having an inlet duct 3
and an outlet duct 4 which is separated from the inlet duct 3 by a
partition 5 in which a cylindrical bore 6 is formed. At one of the
ends of the bore 6, a circular seat 7 is formed for a moving valve
member 8. Control means 9 enables the valve member 8 to be
displaced axially, i.e. in the axial direction of the bore 6 and of
the circular seat 7, between a first position (shown in FIG. 1) in
which the valve 1 is closed, and a second position in which the
valve 1 is open. The valve member 8 can be placed in any desired
position between its first and second positions by the control
means 9.
In the embodiment shown, the control means 9 is constituted by an
electromagnet that is essentially composed of a solenoid 11, a
fixed magnetic circuit or yoke 12, and a moving core 13 inside the
solenoid 11. The yoke 12 and the core 13 form the poles of the
electromagnet 9 and they are designed to drive the core 13 with
displacement that is proportional to the magnitude of the exciting
current as provided by a power supply (not shown). The core 13 is
connected to the valve member 8 by a rod 14.
In the case where the exciting power delivers approximate AC, a
damper 15 is provided to dampen the oscillations of the valve
member 8. The damper 15 is essentially composed of a cylinder 16
which coaxially surrounds the rod 14 and which is filled with oil,
and a piston 17 which is carried by the rod 14 and which divides
the inside volume of the cylinder 16 into a top chamber and a
bottom chamber. A helical spring 18 placed in the top chamber of
the cylinder 16 pushes the piston 17 downwards and consequently
holds the valve member 8 in sealed contact with the seat 7 in the
absence of any exciting current. A sealed bellows 19, which is
fixed firstly to the rod 14 and secondly to the bottom end of the
cylinder 16, separates the inlet duct 3 from the bottom chamber of
the cylinder 16 of the oil-containing damper.
The above-described electrically-controlled valve 1 is entirely
conventional and it is not considered useful to describe it in
further detail, given that it is possible to refer to patent FR-A-2
650 362 or to patent U.S. Pat. No. 3,108,777, both of which are
hereby incorporated by reference in their entirety.
The valve member 8 is composed, in manner known per se, of two
portions 8a and 8b. The portion 8a, which can, for example, be
constituted by a metal dish, open downwards and containing a
sealing gasket made of rubber, for example, serves as a closure
element in the sense that, in the absence of the electromagnet
being excited, the portion 8a is pressed in leakproof manner
against the circular seat 7 so as to close the valve and prevent
any fluid from flowing through the bore 6 from the inlet duct 3 to
the outlet duct 4. When the electrically-controlled valve 1 is
open, i.e. when the portion 8a of the valve member 8 is moved away
from the seat 7, the portion 8b of the valve member 8 serves to
regulate the flowrate of the fluid which flows towards the outlet
duct 4, as a function of the axial position of the valve member 8
relative to the seat 7.
In the valve of the invention, the portion 8b of the valve member 8
is detached from the portion 8a with which it is merely held in
contact, e.g. by means of a spring 21 such as a helical compression
spring having one end which bears against an internal wall 22 of
the body 2 and another end which bears axially against the portion
8b of the valve member 8 in a manner which is described below.
Furthermore, in the present invention, the portion 8b of the valve
member 8 is in the form of a cylindrical part having a cylindrical
outside surface of diameter that is slightly smaller than the
inside diameter of the bore 6, such that the cylindrical part
constituting the portion 8b of the valve member 8 can slide in the
bore 6 with practically no radial play and with no friction.
Thus, it is clear that when the portion 8a of the valve member 8 is
moved away from the seat 7 by being displaced upwards by the
electromagnet 9, the portion 8b of the valve member 8 is also
displaced upwards by the spring 21, thereby remaining in contact
with the portion 8a of the valve member. Conversely, when the
portion 8a of the valve member is lowered in the direction of the
seat 7, it pushes the portion 8b of the valve member downwards,
thereby compressing the spring 21. It can thus be seen that the two
portions 8a and 8b of the valve member can be displaced axially
simultaneously and by the same amount under the combined action of
the electromagnet 9 and of the spring 21. It can also be seen that
it is not necessary for the rod 14 to be accurately in alignment
with the axis of the circular seat 7 or with the axis of the
cylindrical part constituting the portion 8b of the valve member in
order for the system to function correctly.
At least one recess 23 is formed in the cylindrical outside surface
of the part constituting the portion 8b of the valve member 8. The
recess 23 is formed so as to define a passage having a predefined
shape so that a flow of fluid is obtained having a flowrate that is
predetermined as a function of the axial position of the valve
member 8 relative to the seat 7.
FIGS. 2 to 5 show a first embodiment of the cylindrical part
constituting the portion 8b of the valve member 8. The part 8b
shown in FIGS. 2 to 5 is essentially constituted by a hollow
cylindrical element which includes a plurality of longitudinal
slots or notches 23, e.g. six notches 23, which are uniformly
distributed angularly over its peripheral surface. More precisely,
as is visible more particularly in FIGS. 2 to 4, each notch 23 can
include three successive portions 24, 25, and 26 following on from
one another from the top end of the part 8b of the valve member 8
to the bottom end thereof. The top portion 24 of the notch 23,
which has an axial length l.sub.1, has a width which increases
relatively slowly from the top end of the part 8b downwards, i.e.
seen from the outside, the top portion 24 of the notch 23 is an
upsidedown V-shape with an acute angle. The cross-section of the
portion 24 of the notch 23 is also V-shaped and open towards the
outside of the portion 8b, as shown in FIG. 4. Furthermore, the
portion 24 of the notch 23 has a depth which increases from a zero
value, substantially at the top end of the part 8b, to a
predetermined value e.sub.1 in the region where the portion 25 of
the notch 23 begins, as shown in FIG. 3. The portion 25 of the
notch 23, which has an axial length 12, has a width which increases
significantly faster than that of the portion 24. In other words,
seen from the outside of the part 8b, the portion 24 has a
.relatively pointed roof shape (acute angle .alpha.), while the
portion 25 has a relatively flat roof shape. Finally, the third
portion 26 of the notch 23, which can extend over the remaining
length of the part 8b, has a constant width and a constant depth
over its entire length. As shown in FIG. 4, the bases of the
portions 26 of all the notches 23 are formed by cylindrical
surfaces and the portions 26 of the notches 23 are separated from
one another by longitudinal ribs 27 having constant width e.sub.2.
A wide opening 28 is formed in the base of the portion 25 and in
the top portion of the base of the portion 26 of each notch 23, as
shown in FIGS. 2, 3, and 5.
As shown in FIGS. 4 and 5, a plurality of hook-shaped tabs 29, e.g.
six tabs 29, project radially over the inside cylindrical surface
of the cylindrical part 8b. The tabs 29 together form both abutment
means and centering means for the top end of the spring 21 which
pushes the portion 8b of the valve member 8 into contact with the
portion 8a of said valve member.
By way of example, in the case where the bore 6 has an inside
diameter of 13 mm, the dimensions .O slashed.1, .O slashed.2, .O
slashed.3, .O slashed.4, l.sub.1, l.sub.2, e.sub.1, e.sub.2, and
.alpha. can have the following values:
.phi.1 .apprxeq. 12.9 mm .phi.2 = 11 mm l.sub.1 = 1 mm .phi.3 = 10
mm l.sub.2 = 1 mm .phi.4 = 8 mm e.sub.1 = 2 mm .alpha. = 60.degree.
e.sub.2 = 1 mm
In FIG. 6, curve A shows the flow/displacement characteristic
obtained with the electrically-controlled valve of FIGS. 1 to 5,
whose part 8b has the dimensions indicated above, when the
electrically-controlled valve is fed with gas and when its valve
member 8 is displaced by the electromagnet 9 from the position
shown in FIG. 1, in which the electrically-controlled valve is
closed, to a position in which the portion 8a of the valve member 8
is moved away from the seat 7 by three millimeters. As can be seen
in FIG. 6, when the portion 8a of the valve member 8 is still very
close to the seat 7 (less than 1 mm), i.e. in the low-flowrate
range, the flowrate of the gas varies very little with displacement
of the valve member. This is particularly favorable in the case of
an electrically-controlled valve modulating the flow of gas sent to
the burner of a boiler, since the flame of the burner can remain
stable even if the electromagnet 9 of the electrically-controlled
valve is powered with AC.
FIGS. 7 and 8 show another embodiment of the invention, in which
the portion 8b of the valve member 8 is, in this case, constituted
by a solid cylindrical element including two longitudinal recesses
or grooves 23 formed in diametrically opposite positions in its
outside peripheral surface. In this case, each longitudinal groove
23 has a V-shaped cross-section over the entire length of the
portion 8b of the valve member, with a depth which increases
linearly from a zero value to a predefined value from the top end
to the bottom end of the cylindrical part 8b (FIG. 7). With such a
cylindrical part 8b, a flow/displacement characteristic B is
obtained which is linear, as shown in FIG. 9.
In addition, in the embodiment in FIG. 7, instead of using a spring
as means for holding the portion 8b of the valve member 8 in
contact with the portion 8a of said valve member, in this case, a
permanent magnet 31 is used. The magnet 31 can, for example, be in
the form of a disk which is carried by the portion 8a of the valve
member 8. In this case, the portion 8b must be made, at least in
part, of a magnetizable material. Naturally, it is also possible to
have the reverse arrangement. For example, the permanent magnet
could be constituted by a magnetic bar embedded in the central
position in the portion 8b of the valve member, the portion 8a of
said valve member thus being made of a magnetizable material in its
central portion.
The portion 8b of the valve member shown in FIG. 10 has, like that
shown in FIG. 8, two longitudinal recesses or grooves 23 formed in
diametrically opposite positions in its peripheral surface, each
groove 23 having a V-shaped cross-section. However, in the portion
8b of FIG. 10, each groove 23 has, in its top portion 23a, a width
which increases linearly at a slower rate than in the bottom
portion 23b of the groove 23, such that a flow/displacement
characteristic is obtained having the form shown by Curve C in FIG.
11.
In the embodiment shown in FIGS. 12 and 13, the portion 8b of the
valve member 8 is again made in the form of a solid cylindrical
part which is held in contact with the portion 8a of the valve
member by a permanent magnet 31. In this embodiment, the portion 8b
of the valve member differs from those which are shown in FIGS. 8
and 10 in that, in this case, each of the two longitudinal grooves
23 has a width and a depth which are constant over the entire
length of the portion 8b. A flow/displacement characteristic is
thus obtained having the form shown by Curve D in FIG. 14.
Naturally, the above-described embodiments of the present invention
are given purely by way of non-limiting, indicative example, and
numerous modifications can easily be brought thereto by the person
skilled in the art, without going beyond the ambit of the
invention. In particular, the flow direction of the fluid inside
the electrically-controlled valve 1 could be the opposite to that
shown, the duct 4 thus being the inlet duct and the duct 3 the
outlet duct. Furthermore, the hydraulic damper 15 can be replaced
by a pneumatic damper. Furthermore, instead of using an
electromagnet to control the valve member 8 of the valve, other
linear actuators could be used, e.g. an worm-screw and nut system
driven by a reversible electric motor, or even any other control
means, including purely mechanical means, capable of producing
linear displacement of the valve member 8. The present invention is
applicable to any type of valve whose valve member is axially
movable relative to a circular seat as soon as it is desired to
obtain a predefined flow/displacement characteristic, with high
precision, without it being necessary for the valve member 8 and
its control rod 14 to be centered perfectly relative to the axis of
the seat 7.
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